Introduction: Forge

About: I'm a born again Christian. I'm going to school for mechanical engineering at South Dakota State University. I enjoy math, making things, drawing in my notebook, climbing trees, and watching Ironman.

In my first instructable I'm going to show you how I made a forge. I hope it gives you some ideas. Please note that this is just one of many ways to do this, and improvisation is the key to making something that you really love.

Step 1: Assemble Your Supplies


- Chopsaw

- Handsaw

- Drill

- Hammer

- Hand plane

- File

- Tape measure

- Pencil

- Buckets for mold

- Bucket for mixing

- Mold for the vent cover


- (1) 4x4x8 post

- (3) 2x4's

- (About 100) 3 inch outdoor nails

- Outdoor wood glue

- 4 cement blocks

- Plaster of paris

- Clean sand

- Cold water

- Blower

- Paracord

Step 2: Cut Your Boards

I cut four, 2 foot pieces of the 4x4x8 post, and eight, 17 inch pieces of the 2x4's. Save your scrap, because it will come in handy later.

Step 3: Assemble the Stand

First, I nailed and glued a smaller board on the side of two post pieces,( you will want to pre-drill your pieces, I thought it would be fun to just whack a nail in and I paid for it.) I repeated this, and then joined the two halves together with smaller boards on the side.

Next, I cut notches in four of my smaller boards and nailed them into place. These boards are really crucial weight bearers and it is much better for them to fit tightly than to be lose.

Next, I nailed and glued another ring of smaller boards below the top, spaced a 2x4's width down. This will help keep the legs straight and steady.

Finally, I evened out the wobbly legs by glueing and nailing two thin pieces of 2x4 to the bottom. I used a hand planer to flatten out the slightly un-even top, and I filed down some of the sharp edges so they looked nicer and so they wouldn't snag.

Step 4: Cast Your Forge

The shape of your forge will be determined by what buckets or other things that you use as a mold. I made mine circular with 2 1/4 inch thick sides and 2 1/2 inch thick bottom. It is 17 inches across,( just because that was the width of the bucket I had laying around), and 12 1/2 inches wide on the inside. The mold for the vent cover I made out of a roll of duct tape and a can lid taped together to make a circular and somewhat thick vent cover.

I poured the plaster, sand, and water, into a bucket and mixed for all I was worth for about three minutes. I used a 1 to 1 to 1 ratio of plaster, sand, and cold water. If I do this again, I will probably use a 1 to 1 to 2/3 ratio. This mix I poured into my mold and it set up surprisingly fast while I held the inner bucket in place. I also filled the mold for the vent cover.

After about one hour I took out the inner bucket and I removed the plaster from the mold for the vent cover. I gave the larger mold about another half hour because I wanted it to harden up a bit more. I was concerned that it might crumble under it's own weight.

After this half hour, I cut away the bucket with my knife. I lifted the forge on top of it's stand to dry faster. I had a feeling that it was still fragile so I was extra careful. I then rounded off the edges and bumps with my file, and cut three blocks with 45 degree angles and glued and nailed them around the forge. I only used three blocks so that I can slide the monstrous forge off, instead of having to lift it off.

Step 5: Add Your Blower

The first thing I did to add an air supply was to pre-drill a hole in the center of the forge. Then I widened the hole with an inch wide paddle bit. Then I used my chisel to make two wide and fairly deep groves in the vent cover. These are so that air can come out from beneath it, while the cover stops charcoal and ash from falling down the blower hole. If/when I use this as a foundry, I will probably take off this cover as it limits air flow.

For the forge's air flow, I chose to install a leaf blower. I had to take the forge off of it's stand and take the stand out of it's cement blocks. I then tied the leaf blower to a main post with paracord with it's nozzle facing close to the hole in the forge. I re-assembled it all, and finally it is done!

I will not run it with full blown heat for several weeks, because it is still slightly soft and it is so thick that I want to be sure that there isn't any water in it so that it won't blow up.



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    46 Discussions

    could this forge design be used for knife making, like the heat treating process to harden it.


    2 years ago

    I made the mini foundry for the king of random. Works excellent. He's also got some other cool diy projects and ideas I've done. But will be making a bigger one to do some metal working other than melting cans into mini muffin pans.

    1 reply

    Be careful with that one. I made the same one and it overheated while I was making a knife turned to powder

    The firepot is too deep. Also, you will need something for longer pieces of stock to rest on. Heat transfer through the firepot will possible lead to scorching the wood or setting afire.

    How's the plaster/sand mix working out? How durable has it been?

    2 replies

    I did a smaller version back in the spring with the plaster sand mix. Melted about 100 coke cans. Worked extremely well. Used a empty propane torch bottle for my crucible. Out side of forge didn't heat to bad. But kept it in the metal pail I used as a mold. No cracks or anything so far.

    Unfortunately, it has been too windy and rainy to fire my forge yet, I'll let you know when I do. It seems to have become harder and stronger just by air drying these few days. As for durability, it has been great (no chipping or cracking). I just keep it covered when it is going to rain.

    Just out of curiosity couldn't you use an old vacuum motor and secure it permanently rather than propping up the leaf blower (I'd hate melting it). Good work!

    5 replies

    I made a smaller version of this with a hair dryer as my blower. Melted cans with. Burned my hair dryer motor up. Lol. Was going to try using a air mattress one next time. And make a bigger forge to work some steel with to make a large blade/knife ect. With.

    That is a great idea. If I had an old vacuum that I could take apart, I would definitely love to use it and make the blower system a bit more permanent.

    you could use an edf turbine for rc jets you can get awesome thrust from a cheap one and have it variable tuned with an esc and servo tester

    The first forge I worked with had a vacuum for the blower. Did an excellent job. It was my first experience with metalwork. I see old vacuums set out for trash pickup pretty often, sometimes with nothing actually wrong with them...

    Really beautiful work! I love seeing a perfectionist's craftsmanship. :) Hope you get a chance to break it in, soon!

    1 reply

    I made a backyard forge a long time ago. I used a brake drum from a truck and used standard pipe fittings for air. A 'T' fitting let you clean it out pretty easily. The stand was made out of rebar.
    Good job.

    You can use chimney flue repair compound in place of the plaster for higher heat resistance. You can also add vermiculite, perlite, granules of charcoal or any other insulating granules that trap air as an insulator to contain the heat and keep the outside of the forge cooler. I have also used 25# per cubic foot insulating bricks for forge bottom and walls the same way. It's also possible to substitute a blow dryer for the leaf blower. In any case your project is really nice work.

    2 replies

    nice looking fordge indeed!

    the first mixture of compounds I seen used well was:

    perlite, sodium silicate, water, aluminum oxide,

    seen here:

    This trashcan forge looks like a glory hole we use for working with furnace glass shaping! Is it open on both ends?

    Hello, I'm learning about forges at the moment and I'm wondering if anybody can help me understand what the point of putting a blower/vacuum to the forge is? Why is it necessary?